export default function dialogDrag(el, binding, vnode, oldVnode) {
  const dialogHeaderEl = el.querySelector('.el-dialog__header')
  const dragDom = el.querySelector('.el-dialog')
  dialogHeaderEl.style.cursor = 'move'
  dialogHeaderEl.style.cssText += ';cursor:move;'
  dragDom.style.cssText += ';top:0px;'

  // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
  const sty = (function () {
    if (window.document.currentStyle) {
      return (dom, attr) => dom.currentStyle[attr]
    } else {
      return (dom, attr) => getComputedStyle(dom, false)[attr]
    }
  })()

  dialogHeaderEl.onmousedown = (e) => {
    // 鼠标按下，计算当前元素距离可视区的距离
    const disX = e.clientX - dialogHeaderEl.offsetLeft
    const disY = e.clientY - dialogHeaderEl.offsetTop

    const screenWidth = document.documentElement.clientWidth // body当前宽度
    const screenHeight = document.documentElement.clientHeight // 可见区域高度(应为body高度，可某些环境下无法获取)

    const dragDomWidth = dragDom.offsetWidth // 对话框宽度
    const dragDomheight = dragDom.offsetHeight // 对话框高度

    const minDragDomLeft = dragDom.offsetLeft
    const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth

    const minDragDomTop = dragDom.offsetTop
    const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight

    // 获取到的值带px 正则匹配替换
    let styL = sty(dragDom, 'left')
    let styT = sty(dragDom, 'top')

    // 兼容360浏览器低版本左右拖动效果
    styL = (styL === 'auto' || !styL) ? '0px' : styL

    // 注意在ie中 第一次获取到的值为组件自带50% 移动之后赋值为px
    if (styL.includes('%')) {
      styL = +document.body.clientWidth * (+styL.replace(/%/g, '') / 100)
      styT = +document.body.clientHeight * (+styT.replace(/%/g, '') / 100)
    } else {
      styL = +styL.replace(/px/g, '')
      styT = +styT.replace(/px/g, '')
    }

    document.onmousemove = function (e) {
      // 通过事件委托，计算移动的距离
      let left = e.clientX - disX
      let top = e.clientY - disY

      // 边界处理
      if (-(left) > minDragDomLeft) {
        left = -(minDragDomLeft)
      } else if (left > maxDragDomLeft) {
        left = maxDragDomLeft
      }

      if (-(top) > minDragDomTop) {
        top = -(minDragDomTop)
      } else if (top > maxDragDomTop) {
        top = maxDragDomTop
      }

      // 移动当前元素
      dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`
    }

    document.onmouseup = function (e) {
      document.onmousemove = null
      document.onmouseup = null
    }
  }
}
